<!DOCTYPE html>
<html>
<head>
    <title>Simple Page With Text</title>
    <style>
    h1 {
        background-color: #0080ff
    }
    h2 {
        background-color: #00ff80
    }
    </style>
    <script>
        "use strict";

        // Updates the countdown timer value by 1 to 1000
        var timer = () => {
            var textBlock = document.getElementById("timer");
            const countdown_limit = 1000;

            for (var i = 1; i <= countdown_limit; i++)
            {
                textBlock.innerHTML = i;  // update the counter value
            }
            return parseInt(textBlock.innerHTML, 10);  //return the int value which will eventually get converted to string anyways
        };

        function navigateToInvalidPage()
        {
            window.location.assign('http://www.blockedbynavigationstarting.invalid');
        }
    </script>
</head>
<body>
    <h1>Countdown timer</h1>
    Return : <h2 id="timer">0</h2>
    <input id="button" type="submit" name="button" class="largeButton" onclick="navigateToInvalidPage();" value="Navigate Locally" />
</body>
</html>